The present invention relates to a wafer support used for fixing a semiconductor wafer in a processing room of device production apparatus, a method for producing such a wafer support and a method of using such a wafer support.
With the recent remarkable popularization of personal computers, game machines and cellular phones as consumer products, demands for cost reduction in semiconductor device production have been growing. For achieving the cost reduction, improvement in production yield of semiconductor devices is required.
One of factors responsible for a drop in production yield of semiconductor devices consists in a problem that particles adhere to the front or/and rear surfaces of wafer in the production process. As these particles cause breaks in circuits and insulation faults in electrical insulating films, the reduction thereof is strongly desired.
Although wafer supports are used for fixing wafers in a device production apparatus, such as an exposure apparatus, an ion injection apparatus, an etching apparatus, a CVD apparatus, a sputter apparatus or a burn-in apparatus, it is required of the supports to have many other important abilities, including an ability to ensure accurate registration of wafers, an ability to correct the warpage of wafers and an ability to maintain the wafer temperature uniform. Examples of a wafer support which has so far been proposed and used in practice include a ceramic support equipped with a clamping mechanism, a metallic support equipped with a clamping mechanism, a support comprising a base made of ceramic and/or metal, a silicone rubber laminated on 5 the base surface and a clamping mechanism, and an electrostatic chuck (See, e.g., U.S. Pat. No. 4,832,781 and Japanese Tokkai Sho 63-193450). In particular, the support having a silicone rubber laminated ceramic or metallic base is widely used because of its relatively low price and excellent temperature maintaining capability.
However, the support having silicone rubber laminated on the surface of a base made of ceramic and/or metal has a problem that, in the conventional case where the support is made in a clean room, washed with purified water and packed directly in a plastic film bag, slippages occur between the film surface and the silicone rubber surface during transport to form particles from both silicone rubber and plastic film by friction between them. Further, such a wafer support has another problem that, when the wafer support is installed in the device production apparatus as recited above, the operator is required to prevent pollution of the silicone rubber surface of the wafer support by impurities in the air and perform the installation work without touching the silicone rubber surface; as a result, the workability is markedly lowered.
As a result of our intensive studies for resolving the aforementioned problems, it has been found that the formation of particles during transport and the pollution caused during the installation work can be prevented by providing a special dustproof covering film on the silicon rubber surface of a wafer support of the type which has the silicone rubber layer on a base made of ceramic and/or metal and peeling the dustproof covering film apart from the silicone rubber layer immediately before use, and a method for producing a pollution-free wafer support at a low price has been developed, thereby achieving the present invention.
More specifically, a first subject matter of the present invention is a dustproof covering film-attached wafer support comprising a base, a silicone rubber layer substantially uniform in thickness and integrated with the base and a dustproof covering film, wherein the covering film is attached to the silicone rubber layer in a state that the covering film is capable of being peeled apart from the silicone rubber layer and the peel strength between the covering film and the silicone rubber layer is from 5 to 500 g/25 mm, measured by the peeling test according to JIS K 6854.
A second subject matter of the invention is a method for producing a dustproof covering film-attached wafer support, comprising the following steps (A) to (D):
(A) a step of forming a silicone rubber layer substantially uniform in thickness on a process sheet having a surface roughness (Ra) of 0.1 to 5.0 xcexcm which functions as a dustproof covering film,
(B) a step of forming the silicone rubber layer into a desired shape and boring guide holes for registration in the process sheet,
(C) a step of applying an adhesive to one surface of a base, and
(D) a step of sticking the silicone rubber layer formed on the process sheet to the adhesive-applied base surface, wherein the guide holes bored in the process sheet are used for properly positioning the silicone rubber layer on the base.
A third subject matter of the invention is a method of using a dustproof covering film-attached wafer support as described in the first subject matter, comprising a step of peeling the dustproof covering film apart from the silicone rubber layer in the processing room of a device production apparatus selected from a group consisting of an exposure apparatus, an ion injector, an etching apparatus, a CVD apparatus, a sputtering apparatus and a burn-in apparatus, and a step of fixing a semiconductor wafer onto the silicone rubber layer of the wafer support.